Marine Algce of the Orkney Islands. 309 



PUNCTARIA, Greville. 



42. Punctaria tenuissima, Grev. 



Epiphytic on " Laminaria," according to Dr ^I'Bain, in Calf 

 Sound, 4 fathoms, rare ; also in Kirkwall Eay, according to Mr 

 Pollexfen. Annual. Summer. 



43. Punctaria latifolia, Grev. 



On rocks and stones in deep water. Annual. Summer. Calf 

 Soiind, 4 fathoms, rare ; Eousay, cast ashore. 



44. Punctaria plantaginea (Roth), Grev. 



On rocks and stones in pools between tide marks ; occasionally 

 epiphytic on Alg£)e. Always submerged. Annual. Summer and 

 autumn. Calf Sound, 4 fathoms ; Eousay. 



STRIARIA, Greville. 



45. Striaria attenuata, Grev. 



Epiphytic on the smaller Algae in deep water. Annual. Summer. 

 Found by Mr Pollexfen in Damsay Bay and Kirkwall Bay. Cast 

 ashore in Eousay. 



Family.— DESMAEESTIACE^. 



DESMARESTIA, Lamour. 



46. Desmarestia aculeata (Linn.), Lamour. 



On stones and rocks from a little below the low-water mark of 

 spring tides to deep water. Perennial. Calf Sound, 4 fathoms, 

 stony bottom ; Kirkwall Bay, off Crossiecrown, 5i fathoms ; and, 

 generally, in sheltered bays, sandy and coral bottoms. 



47. Desmarestia ligulata (Lightf. ), Lamour. 



In rock pools near low-water mark, and at a greater depth. 

 Annual. Summer. Grows to the height of from 20 to 30 inches. 

 North Shore, Westray, fine (J. W. Gray). Mr Pollexfen has dredged 

 very fine specimens in Kirkwall Bay ; but by far the largest he has 

 ever seen were found at Skaill, West ^Mainland. Occurs also at 

 Skaill, in Eousay. 



48. Desmarestia viridis {FL Dan.), Lamour. 



On stones and rocks from a little below the low-water mark of 

 spring tides to deep water. Perennial. Kirkwall Bay, oS Crossie- 

 crown, 5i fathoms; Eousay; Deer Sound, 15 fathoms, very fine ; 

 "Pentland Firth, 40 fathoms, when dredging for Zoophytes" 

 (M'Bain). 



Family.— DICTYOSIPHON'ACEiE. 



DICTYOSIPHON, Grev. 



49. Dictyosiphon foeniculaceus (Huds.), Grev. 



Common in pools at about half-tide level, epiphytic on Scytosiphon 

 lomentarius, and other small Algce. Always submerged. Annual. 

 April to October. Spores escape in July and August. 



